The invention relates to a spray nozzle for dispensing a liquid, which is subject to an elevated pressure, in the form of a spray comprising
(A) a housing having a central nozzle outlet and a central nozzle axis therethrough, and PA0 (B) a hollow nozzle interior which is surrounded by a side wall, and through which liquid flows towards the nozzle outlet, and which interior comprises
(a) a discharge chamber located upstream of the nozzle outlet on the inside and arranged coaxially with, and along a central plane perpendicular to, the central axis of the nozzle,
(b) an annular chamber arranged coaxially to the discharge chamber,
(c) at least two feed channels which connect the annular chamber to the discharge chamber, which lead to the latter at least approximately tangentially to the periphery of the discharge chamber and which each run in a plane intersecting the central axis of the nozzle, the feed channels and the annular chamber forming a first stage of turbulence, and
(d) at least one supply duct for feeding liquid to the first stage of turbulence from a supply line for the liquid.
Moreover, the invention relates to devices in which the new spray nozzle is used, and to processes for the manufacture thereof.
A spray nozzle of the type initially set forth has been disclosed in U.S. Pat. No. 3,652,018 by John Richard Focht and is used for the mechanical "break-up" of a liquid stream, a spray mist of droplets being formed. This known nozzle is easier to manufacture than a nozzle which is designed to have similar basic features and is described in U.S. Pat. No. 3,083,917 by Robert Abplanalp et al. The feed channels of the known Focht nozzle are separated from one another by separating elements, such as baffles; they start from a common outer annular chamber and end in a common central outlet orifice.
The arrangement of four feed channels which, starting from an outer annular chamber, tangentially open in the wall of a central cylindrical mixing chamber in order to effect an improved atomization of liquid material, has also been disclosed already in U.S. Pat. No. 1,594,641 by Fletcher Coleman Starr in 1926.
U.S. Pat. No. 2,503,481 to William W. Hallinan and No. 3,692,245 to Arthur Michael Needham et al. and British Pat. No. 320,567 to Gustav Schlick also show feed channels which start at the periphery of a frustoconical surface which is tapered toward a nozzle outlet and ends in a flat frontal face opposite the outlet. In the frustoconical surface there are provided grooves forming fluid channels which extend in a curved configuration to the front face and have their outlet openings in the latter face, any obstacle to fluid flow through these channels being carefully avoided or eliminated.
However, these known spray nozzles do not adequately meet the requirements which have to be fulfilled by many products to be sprayed, such as hair lacquer, deodorants, air fresheners or insecticides. Thus, they should have a particle size between 5 and 10.mu., for example particularly in the case of hair lacquer, in order to obtain a rapid evaporation period, so that matting of strands of hair is avoided when the consumer pats the set into place after spraying. Air fresheners and insecticides must evaporate rapidly or float in the air so that they do not stain furniture, walls, carpets or parquet floors. In spite of a very fine particle size, the sprayed product must also possess a sufficiently strong impingement force, in the case of hair lacquer, so that the latter not only comes to lie on the hair but can also penetrate in between which ensures an airy set. In the case of air fresheners and insecticides, the spray mist should penetrate as far as possible into the air space to be treated. (The short term "cross section" is used hereinafter for "cross sectional area").
Commercially available spray nozzles such as are available for aerosol cans or pump atomizers, require a pressure of at least 6 atmospheres gauge for producing spray mists of the said quality, when they are used without a liquefied gas component, or they require about 3 atmospheres gauge when such a component is present since, as is known, a propellant consisting of liquefied gas is pressure-relieved in contact with the surrounding air and thus decisively contributes to the formation of the fine droplet size in the spray mist.